I remember a LONG time ago on a boys out camping trip, me and a friend of mine were walking around our camp. It had just rained, and some first-year scouts hadn't set up their mini-camp right, so they got soaked and had to move into one of our troop's private trailers (simple cargo trailer, box shape, 8x8ft roughly.)
They tend to be idiots and shout obscenities like 6th graders do, so me and my buddy decided we would close the trailer door, put the padlock on and lock it (we both knew the combo to unlock the trailer, we just wanted to hear them freak out, they screamed bloody murder, gay love and cannibalism for a good 10 minutes.)
However, my idiot friend hadn't fully adjuste his eyes to the darkness (it was quite literally pitch black), and he ran into a post about 1.5ft tall, aka he caught it with his nuts. He went down on one knee in a dry spot, got up after a bit of laughing, and ran into it again. This caught the attention of the younger scouts, and they started taunting my friend.
At that, he tried ONE last time. Guess.
Post to the balls for a 3rd time.
So at this point I just went up and did it myself, laughed at my friend, we walked off to get a soda for each of us from my camp, then we came back (with him standing behind me so he wouldn't hit the sign again) and unlocked the trailer.
Doorknobs hurt? So does getting your hand stuck in a car door.
Or smashing your nuts against a wooden post 3 times in a row within a 2 minute time frame